Continuous casting



April 14, 1970 R. J. DAIN CONTINUOUS CASTING s sheets-sheet 1 Filed May 18, 1967 INVENTOR R'. I. DMN

Mwhwlwluin/Ms ATTORNEYS April 14, 1970 R. J. DAIN CONTINUOUS CASTING 3 Sheets-Sheet 2 Filed May 18, 1967 um mv WHW l@ r l 1- sv a @V INVENTOR BY R. J. 'DMN MWL.

'uvois ATTORNEYS April 14, 1970 R.J.DA1N A3,506,063

CON'IINUOUS CASTING Filed May 18, 1967 3 Sheets-Sheet 5 INVENTOR ATTORNEYS United States Patent 3,506,063 CNTINUOUS CASTING Richard James Dain, Tonbridge, England, assignor to Ashmore, Benson, Pease & Company Limited, Stockton-on-Tees, England Filed May 18, 1967, Ser. No. 639,543 Int. Cl. B22d 11/10 U.S. Cl. 164-281 1 Claim ABSTRACT 0F THE DISCLOSURE The disclosure is concerned with continuous casting of metals particularly steel and provides a two part mould, the upstream part of which is made of graphite and the major downstream part of which is made of a high conductivity material. The metal being cast is supplied to the mould by a supply means which is reciprocable with the mould so that the meniscus of molten metal is maintained in the graphite part where the molten metal initially starts to freeze onto the mould walls.

This invention relates to continuous casting of metals particularly steel.

Generally moulds for continuous casting are formed of either graphite or a metal such as copper or copper alloys having a high conductivity and high durability. The mould is subjected to high temperatures which are applied suddenly as molten metal enters the mould and which temperatures vary along the length of the mould so that the expansion of the mould differs along its length. With an entirely metal mould distortion and buckling occurs so that it is necessary to change the mould after each cast or at least every few casts. While graphite is less subject to distortion it does not always provide suicient removal of heat especially when casting metals with a high melting point such as steel.

It is also known that sticking of the metal being cast to the walls of the mould can cause tearing of the newly formed skin and consequent break-out of molten metal and it is known to obviate this by reciprocation of the mo-uld parallel to its axis.

In one aspect the present invention provides apparatus for continuous or semi-continuous casting of metal comprising an open ended mould, the mould channel of which is a substantially continuous cross-section, means for supplying molten metal to the upstream end of the mould channel, means for withdrawing solidified metal from the downstream end of the mould, and means for reciproeating the mould parallel to the axis thereof during casting, the mould being formed in two parts of which the upstream part is formed of graphite and the downstream part is formed of material having a high conductivity, and means for controlling the temperature of the parts so that solidilication of the metal begins on the walls of the graphite part.

In another aspect the invention provides a method of casting metal which comprises continuously supplying molten metal into the open ended mould the upstream end of which is made of graphite at the downstream end of which is made of a material having a high conductivity, continually withdrawing solidified metal from the downstream end of the mould, and which includes controlling the temperature of the mould parts and the casting speed so that solidilication of metal starts against the graphite walls of the mould and the meniscus level of molten metal is maintained in the graphite part and including reciprocating the mould to prevent sticking to the mould Walls.

The highest heat transfer takes place at meniscus level. When :using a metal/graphite mould distortion of the mould at this point is avoided so that the metal part will 3,506,063 Patented Apr. 14, 1970 have an increased life while sufficient heat removal is provided in the majority of the mould by using a high conductivity materal. The graphite part provides good lubrication in the area in which the skin of the cast is first formed and can be replaced after each cast if necessary to allow for erosion. In one form the axis of the mould is horizontal and the mould and tundish are horizontally reciprocable.

The inner surface of the metal part is preferably covered with a metallic spray coating and impregnated before each cast with for example a lubricant such as molybdenum disulphide or alternatively an oil which in operation will form graphite deposited'in the spaces between the particles of the coating, which lubricant dressing may be renewed after each cast. Preferably the mould is secured to a horizontally movable trolley and the tundish is mounted on the trolley for horizontal movement parallel to the axis of the mould, means being then provided for continuously urging the tundish against the mould. Preferably the surface of the tundish in engagement with the upstream part of the mould is formed of graphite; the favourable angle of contact between molten metal and graphite ensuring a good seal between the engaging graphite surfaces thus preventing leakage of molten metal. For this purpose graphite inserts may be provided on the tundish.

The tundish preferably has an upwardly facing opening to receive molten metal from a ladle of steel which has preferably been previously degased, thereabove, the opening being sufficiently large to accommodate reciprocation of the tundish.

A dummy bar is horizontally movable into the mould for the start of a cast and preferably has an extending portion designed to plug the exit from the tundish, thus avoiding an internal plug in the tundish.

One embodiment of horizontal continuous casting apparatus, in accordance with the invention, will now be described, by way of example only, with reference to the accompanying drawings of which:

FIGURE 1 is a diagrammatic plan View of the layout of a horizontal slab continuous casting plant,

FIGURE 2 is a side view of the casting apparatus, and

FIGURE 3 is a vertical section through the mould and exit of the tundish.

Referring iirst to FIGURE l the mould and tundish in the casting position are mounted on a trolley 12 beneath a degassed ladle and the slab issuing from the mould is driven by withdrawal rolls 14 along a roller ta-ble 15 through a spray chamber 16 and cutoff shear 17 from which it is transferred sideways to a cooling bank 18 and from thence in the direction of arrow 20 to a slab disposal bay. Dummy bar handling apparatus is provided at 21 Vbeyond the transfer point to the cooling bank 18. An emergency ladle pit is provided at 22 to collect accidentally spilled meal. A degassing station 23 provides cars 24 on which are mounted ladles beside degassing pumps at 25. These ladles are transferred to the position at 13 by a transfer crane 26. Water pumps located at 27 and a cooling tower 28 provide water to the mould and spray chamber. The trolley 12 can be moved away from the casting position along a horizontal track 30 to a position 12a from which it can receive a new tundish from the tundish preparation station 31 or the tundish Preheat station 32. A cross-track 33 connects with the track 30 through a turntable 34 and allows the trolley to be transferred to a further track 35 connected by turntable 36 along =which is situated the casting carriage repair 'bay 37 and a spares store 38. Track 33 also allows a carriage awaiting size change at 40 to be transferred to the track 30. A refractory store is provided at 41 and electrical controls at 42.

Referring now to FIGURES 2 and 3, the trolley 12 is provided with wheels 43 which run on the track 30 parallel to the mould axis. The rearward end of the trolley carries an extension 44 in which a pin 45 is detachably disposed to connect the trolley with a horizontal reciprocation jack 46. This jack may be controlled in known manner to reciprocate the trolley to prevent sticking of the cast material to the mould wall, the reciprocation being either continuous or starting immediately sticking occurs. A horizontal ow-through mould 47 having a mould channel of substantially constant cross-section throughout is firmly secured to the upper surface of the trolley by bolts not shown. A tundish 48 is horizontally slidable parallel to the axis S of the mould on a slide 51 formed on the upper surface of the trolley. A spring loaded device 52 is arranged to permanently urge the tundish against the mould making allowance for thermal expansion. The tundish 48 iS formed of refractory or like material having a high insulation and has an upwardly facing opening 53 through which it receives a stream 54 of molten metal, e.g. steel, from a ladle of degassed metal 54 suspended above the tundish. Also formed in the lid of the tundish is a preheat burner 56 by which the tundish is heated before it is filled With metal. During operation nitrogen or other non-reactive gas is supplied through the burner opening and continuously ows over the metal in the tundish and out through the opening 53 in the direction of arrows 57. The tundish is formed with an outlet 58 of smaller cross-section than the mould channel and coaxial with the axis of the mould, through which molten metal 54 ows to the mould. Referring to FIGURE 3 the form of the outlet 58 is dened by an insert 60 formed of fireclay to prevent freezing in the outlet passage. The mould 47 is formed in two parts; the smaller upstream part 61 being formed of graphite and being bolted by heat resisting bolts 62 having heat resisting belleville washers 63 to the major downstream part 64. The part 64 is made of copper or copper alloy or other suitable metal having high conductivity and durability and is provided with passages 65 for circulation of cooling water in known manner. A passage 66 for circulation of cooling water is also provided in the graphite section 61. The bore of the copper part 64 may be very slightly larger than the bore of the graphite part 61 giving a step down of for example 0.010 to accommodate minor misalignment. The inner surface 67 of the copper portion is provided with a spray coating 68 for example of porous copper particles and a lubricant such as molybdenum disulphide or graphite is deposited in the spaces between the particles of the spray coating. In operation, the casting speed and the temperature of the graphite part of the mould are controlled so that solidification of steel beings against the graphite walls, and the meniscus level is in the graphite part of the mould: the highest heat transfer takes place at meniscus level and normally produces distortion of a copper mould. By using a graphite mould part at the meniscus level, which part will not distort, the copper portion will have increased life. The graphite part can be changed after each cast if necessary.

At the exit end of the insert 60 Zircon stops 70 are secured to the leading wall of the tundish and are provided with graphite inserts 71 which may be replaced as often as necessary. The graphite inserts 71 are urged by the jack 52 against the graphite part 61 of the mould and due to the surface contact angle properties of graphite and molten metal the engaging graphite surfaces form a good seal. An emergency launder 72 is positioned below the engaging surfaces in case of leakage through this seal. At the exit end of the mould the cast slab 73 is moved by withdrawal rolls 14 along the roller table 15 and passes between spring loaded guide rolls 74 and watershields 75 to the spray chamber 16. Cooling water is also sprayed over the cast slab as it passes between the guide rolls 74 and the water shields 75 direct the water, and metal should a break-out occur, to a water sludge pit 76. A dummy bar 77 is arranged to be driven by dummy bar handling means at 21 and by the withdrawal rolls which are reversible along the roller table 15 to enter the mold at the beginning of a cast in the usual manner. The forward end of the dummy bar is provided with an extension 78 secured thereto by pins V80, 81, this extension being designed to stop the opening 58 from the tundish at the commencement of a cast. This obviates the necessity for an internal stop in the tundish. The trolley has connection points 82, 83, 84 for connection to air, preheat fuel, and nitrogen lines respectively, has connection points 85 for connection to mould cooling water supply lines and has connections -86 for connection to secondary cooling water supply lines.

In operation a trolley carrying a preheated tundish and mould is brought to the casting station and a ladle from the degassing station is positioned above the tundish, the dummy bar is introduced into the mould, the ladle is opened to empty into the tundish and a cast is continuously carried out while the trolley is reciprocated, as required, in known manner to prevent sticking of the casting to the mould walls, and the mould and spray chamber are provided with cooling water. After a cast is completed, the pin 45 is taken out to disconnect the trolley from the reciprocation jack and the trolley is removed to a position in which the mould parts 61 and 71 can be replaced by new corresponding parts.

What is claimed is:

1. Apparatus for the continuous casting of metal comprising a mould defining an open ended mould cavity of substantially constant cross-section normal to its longitudinal axis, means for supplying molten metal to one end of the mould cavity, means for withdrawing solidiiied metal from the other end of the cavity, means for causing relative reciproc-ation between the mould and the solidified metal in the direction of the longitudinal axis of the mould cavity, the mould being formed in two parts of which the upstream part is formed of graphite and the downstream part is formed of a material having a -high thermal conductivity, the supply means being movable parallel to the mould 'axis relative to the mould and including means for urging the supply means into engagement with the mould and the edge of the supply means engaging the upstream end of the mould being formed of graphite.

References Cited UNITED STATES PATENTS 944,668 12/1909 Doutier 164-263 1,088,171 2/1914 Pehrson 164-282 X 2,693,624 1l/1954 Corneil 164-268 2,946,100 7/1960 Baier et al. 164-83 3,263,283 8/1966 Allard 164-73 X 3,381,744 5/1968 Taccone 164-295 FOREIGN PATENTS 1,040,273 8/ 1966 Great Britain.

I. SPENCER OVERHOLSER, Primary Examiner J. S. BROWN, Assistant Examiner U.S. Cl. X.R. 164-83 

